spsc example

diff --git a/spsc-example/Makefile b/spsc-example/Makefile
new file mode 100644 (file)
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--- /dev/null
+++ b/spsc-example/Makefile
@@ -0,0 +1,11 @@
+include ../benchmarks.mk
+
+TESTNAME = spsc-queue
+
+all: $(TESTNAME)
+
+$(TESTNAME): $(TESTNAME).cc queue.h
+       $(CXX) -o $@ $< $(CXXFLAGS) $(LDFLAGS)
+
+clean:
+       rm -f $(TESTNAME) *.o

diff --git a/spsc-example/note.txt b/spsc-example/note.txt
new file mode 100644 (file)
index 0000000..c12ab95
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+++ b/spsc-example/note.txt
@@ -0,0 +1,2 @@
+This is the example used in the scfence example section in the paper.
+We need to deal with the problem of data races.

diff --git a/spsc-example/queue.h b/spsc-example/queue.h
new file mode 100644 (file)
index 0000000..76430e7
--- /dev/null
+++ b/spsc-example/queue.h
@@ -0,0 +1,39 @@
+#include <unrelacy.h>
+#include <atomic>
+
+using namespace std;
+
+struct node {
+       node(int d): data(d) {
+               next.store(0, memory_order_relaxed);
+       }
+       atomic<node*> next;
+       int data;
+};
+
+class spsc_queue
+{
+       atomic<node*> head, tail;
+       public:
+       spsc_queue() {
+               head = tail = new node(0);
+       }
+
+       void enqueue(int val) {
+               node* n = new node(val);
+               node *h = head.load(memory_order_relaxed); 
+               h->next.store(n, memory_order_release);
+               head.store(n, memory_order_relaxed);
+       }
+
+       bool dequeue(int *v) {
+               node* t = tail.load(memory_order_relaxed);
+               node* n = t->next.load(memory_order_acquire);
+               if (0 == n)
+                       return false;
+               *v = n->data;
+               tail.store(n, memory_order_relaxed);
+               delete (t);
+               return true;
+       }
+};

diff --git a/spsc-example/spsc-queue.cc b/spsc-example/spsc-queue.cc
new file mode 100644 (file)
index 0000000..cfb34ec
--- /dev/null
+++ b/spsc-example/spsc-queue.cc
@@ -0,0 +1,37 @@
+#include <threads.h>
+
+#include "queue.h"
+
+spsc_queue *q;
+atomic_int arr[2];
+
+void thread(unsigned thread_index)
+{
+       if (0 == thread_index)
+       {
+               arr[1].store(memory_order_relaxed);
+               q->enqueue(1);
+       }
+       else
+       {
+               int val = 0;
+               bool succ = q->dequeue(&val);
+               arr[val].load(memory_order_relaxed);
+       }
+}
+
+int user_main(int argc, char **argv)
+{
+       thrd_t A, B;
+
+       q = new spsc_queue();
+
+       thrd_create(&A, (thrd_start_t)&thread, (void *)0);
+       thrd_create(&B, (thrd_start_t)&thread, (void *)1);
+       thrd_join(A);
+       thrd_join(B);
+
+       delete q;
+
+       return 0;
+}